Ranchers in Mexico are struggling against a flesh-eating parasite infecting livestock

Alfredo Chavez, a cattle rancher and livestock technician, shows New World screwworm larvae removed from a cow at his ranch in Cintalapa, Chiapas, Mexico, on July 23, 2025, amid an infestation that led the U.S. to suspend cattle imports over fears the pest could reach the border.

In the southern state of Chiapas, which borders Guatemala, the New World screwworm fly's rapid spread appears to have caught most ranchers off guard, despite memories of previous outbreaks in the 1980s and 1990s.

(Image credit: Isabel Mateos)